1. Field of the Invention
The present invention relates to address notification, and more particularly relates to an address notifying technique in a network system and a method of notifying an address of a backup apparatus in an IP (Internet Protocol) telephony.
2. Description of the Related Art
As one of features in an IP telephony system, there is a point that a service can be provided from one point to a plurality of sites which are far away. Since this configuration is employed, it is possible to attain integrated management of data. However, simultaneously with this, the service cannot be provided even when any of network apparatuses other than a server and a terminal is failed. For this reason, a backup apparatus is installed in a necessary location in order to continue to provide the service even when the network apparatus is failed.
A method of using this backup apparatus will be described below. At a time of a normal operation, a VoIP (Voice over Internet Protocol) service providing apparatus belonging to a LAN (Local Area Network) provides the service for all terminals containing terminals belonging to the above LAN and terminals belonging to other LANs connected through WAN (Wide Area Network) to the above LAN. Here, the terminal implies an apparatus such as an IP telephone, all the kinds of terminal apparatuses used in the IP telephony, and a Gateway apparatus for conversion between IP channel and a conventional channel.
Now, it is supposed that a failure has occurred in the WAN so that a communication between a VoIP service providing apparatus and a terminal belonging to a LAN cannot be carried out. At this time, if the terminal belonging to the LAN previously obtains an IP address of a VoIP service backup unit or apparatus installed in the other LAN from the VoIP service providing apparatus, the terminal can continue to receive the service from the VoIP service backup apparatus by performing re-registration to the VoIP service backup apparatus.
In the normal operation, it is necessary that the LANs at the respective sites are normal when the WAN is failed. However, a network trouble is not simple, and there is a possibility that the trouble has a spreading compositely. For example, a case could be considered that a failure has occurred in another LAN so that a communication between the VoIP service backup apparatus and a terminal belonging the other LAN is impossible. In such a case, the terminal cannot receive the service even if the VoIP service providing apparatus is provided. At this time, the terminal cannot receive the service, even if there is the VoIP service backup apparatus belonging to another LAN.
In conjunction with the above description, Japanese Laid Open Patent Application (JP-P 2004-186766A) discloses a backup controller. In this conventional example, the backup controller automatically backs up in a remote station, a controller which centrally controls a voice exchange between a plurality of IP telephones in at least one remote station through an IP network. This backup controller has a failure monitoring section, a first automatic switching section and a second automatic switching section. In accordance with a reception state of a periodical transmission signal from a controller or a reception state of an allowable response for the periodical transmission signal to the controller, if those reception states reach a predetermined failure reference, the failure monitoring section determines that a failure has occurred. Moreover, after the failure is determined to have occurred, if those reception states reach a predetermined recovery reference, it is determined that the failure is recovered. If the failure monitoring section determines that the failure is has occurred, the first automatic switching section disconnects the IP telephone in the remote station from the controller, and registers it as a self-extension terminal to set it to be usable. Then, the IP telephone can carry out transmission/reception to/from an extension or a station line. If the failure monitoring section determines that the failure has been recovered, the second automatic switching section disconnects the IP telephone that is registered as the self-extension terminal and made usable, and then re-connects to the controller.
Also, Japanese Laid Open Patent Application (JP-P2004-328604A) discloses an IP telephony service system. In this conventional example, the IP telephony service system in which an IP telephony service providing apparatus provided in a main network is used to attain an IP telephony service for an IP terminal, The main network has an IP telephony service providing apparatus for providing an IF telephony service to an IP terminal; and a first database that is linked with the IP telephony service providing apparatus and stores a service data provided to the IP terminal. Inside a plurality of sub-networks, there are an IP telephony service backup apparatus for providing an IP telephony service, when a communication with the IP telephony service providing apparatus in the main network through the IP terminal becomes impossible; and a second database that is linked with the IP telephony service backup apparatus and stores service data provided to the IP terminal by the IP telephony service backup apparatus.
Also, Japanese Laid Open Patent Application (JP-A-Heisei, 11-308236) discloses an emulated LAN apparatus. In this conventional example, the emulated LAN apparatus is provided with an LES/BUS server and an LAN emulation client. The server is composed of a currently-used server and a spare server, and the client holds an ATM address table corresponding to each server, and when a failure of the currently-used server is detected, its connection is switched to the spare server.